[ncl-talk] can't seem to make my arrows bigger

[Kyle Griffin]

Hi Lesley,

First, please make sure ncl-talk is included in future replies, as others
may also have useful insights.

My next suggestion would be to try unsetting the vcRefMagnitudeF and
vcRefLenghtF - NCL has the ability to calculate these by default to create
a plot that at least looks somewhat reasonable. Although the resultant plot
is not likely to be the results you actually want, you can look at the
settings it chooses and use that as guidance.

Some code like this after the plot is drawn might be insightful:

getvalues plot   ; plot is whatever you have saved your vector plot as,
e.g. plot=gsn_csm_vector(....)
  vcRefMagnitueF : calc_ref_mag
  vcRefLengthF : calc_ref_length
end getvalues

print("Mag: "+calc_ref_mag+"   Length: "+calc_ref_length)


If this doesn't provide the insight you are looking for, please include
your code (even if simplified) and data in a response if you can, using the
NCL FTP site if necessary, and someone can take a look at it. I'm also
wondering if there might be some internal limits to vector size settings,
but at the moment, I can't think of any good reason why this would be the
case (but I'm also not a developer, either).


Kyle

----------------------------------------
Kyle S. Griffin
Department of Atmospheric and Oceanic Sciences
University of Wisconsin - Madison
Room 1421
1225 W Dayton St, Madison, WI 53706
Email: ksgriffin2 at wisc.edu

On Mon, Apr 27, 2015 at 10:38 AM, Lesley Smith - NOAA Affiliate <
lesley.l.smith at noaa.gov> wrote:

> Hi Kyle,
> I appreciate you writing me back.
> I'm plotting meridional and vertical EP flux with my arrows, not winds.
> The values are of magnitude 1.e10 and 1.e8
> For example, meridional_EP_flux: min=-1.6812e+10   max=1.07296e+10
>
> vertical_EP_flux: min=-1.53672e+08   max=1.33486e+08
>
> Thus, my values *are* on the order of  2,000,000,000
>
>
> Your suggestions result in:
>
> fatal:VectorPlotDraw: VVECTR - VECTOR NDC LENGTH TOO GREAT
>
> fatal:VectorPlotDraw: error drawing vectors
>
> fatal:VectorPlotDraw: draw error
>
> fatal:PlotManagerDraw: error in plot draw
>
> fatal:_NhlPlotManagerDraw: Draw error
>
> Do you have any other suggestions?
> Thanks,
> -Lesley
>
> On Fri, Apr 24, 2015 at 7:40 PM, Kyle Griffin <ksgriffin2 at wisc.edu> wrote:
>
>> Hi Lesley,
>>
>> I think you've switched your reference vector settings around. You should
>> be either making vcRefMagnitudeF *smaller* or making vcRefLengthF *larger*.
>> These act in concert to control the size of the vectors in your plot. Each
>> actually controls the magnitude and length of the vector in the reference
>> vector box in the bottom right of your attached image. You'll note that in
>> this current setting, you would need a wind speed of 2,000,000,000 m/s to
>> have a vector plotted at that size. In reality, you might want to set
>> vcRefMagnitudeF to a value somewhere between 10.0 and 50.0. If this still
>> doesn't make your vectors large enough, reduce the vcRefMagnitudeF to 1.0
>> and I'm sure you'll see some EP flux arrows appear. You can always check
>> the max() and min() of your vector field if you aren't sure the actual
>> magnitudes you are dealing with.
>>
>> Let us know if you have any more questions.
>>
>>
>> Kyle
>>
>> ----------------------------------------
>> Kyle S. Griffin
>> Department of Atmospheric and Oceanic Sciences
>> University of Wisconsin - Madison
>> Room 1421
>> 1225 W Dayton St, Madison, WI 53706
>> Email: ksgriffin2 at wisc.edu
>>
>> On Fri, Apr 24, 2015 at 4:20 PM, Lesley Smith - NOAA Affiliate <
>> lesley.l.smith at noaa.gov> wrote:
>>
>>> Hi gang,
>>> I'm using gsn_csm_pres_hgt_vector to make a plot.
>>> In the past it has worked great for me.
>>>
>>> This time, I can't seem to make my arrows big enough to see
>>> anything.  I attach a plot of contoured EP Divergence with the
>>> corresponding 2 EP components in vector form overlaid. The components
>>> are many orders of magnitude greater than the divergence.
>>> I've tried changing vcRefMagnitudeF and vcRefMagnitudeF to
>>> a variety of values and the arrows look the same.
>>> I tried scaling the vertical component (like one of the examples on the
>>> NCL website) to no effect.
>>>
>>> Eventually when I make vcRefMagnitudeF too small it suddenly gives the
>>> error:
>>>
>>> fatal:VectorPlotDraw: VVECTR - VECTOR NDC LENGTH TOO GREAT
>>>
>>> fatal:VectorPlotDraw: error drawing vectors
>>>
>>> fatal:VectorPlotDraw: draw error
>>>
>>> fatal:PlotManagerDraw: error in plot draw
>>>
>>> fatal:_NhlPlotManagerDraw: Draw error
>>>
>>>
>>>
>>> I'd love any suggestions!
>>>
>>> Thanks!
>>>
>>> -Lesley
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> List instructions, subscriber options, unsubscribe:
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>>>
>>>
>>
>
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